1. Field of the Invention
Embodiments of the present invention generally relate to a downhole tool. More particularly, the invention relates to a whipstock retrieval tool. More particularly still, the invention relates to a self aligning retrieval tool configured to automatically engage a whipstock.
2. Description of the Related Art
During a drilling operation of oil and gas wells, a wellbore is formed in the Earth and typically lined with a tubular that is cemented into place to prevent cave in and to facilitate the isolation of certain areas of the wellbore for the collection of hydrocarbons. Once the tubular or casing is cemented into place, the hydrocarbons are typically gathered using a smaller string of tubulars called production tubing. Due to a variety of issues, including depletion of formations adjacent the wellbore and stuck tools and pipe that prevent continued use of the wellbore, it is often desirable to form another wellbore, not from the surface, but from some location along the existing wellbore. This new or lateral wellbore can also be lined with pipe and then hydrocarbons can be collected along its length. It is not uncommon to have more than one lateral or sidetracked wellbore extending from a single central or parent wellbore. Although wellbores are typically cemented with steel pipe or casing, as stated above, a lateral wellbore may also be utilized in an un-cased wellbore.
Initiating a lateral wellbore from a central wellbore requires an opening, hole, or window to be formed in the wall adjacent a location where the lateral wellbore will commence. Forming windows is typically done with the help of a whipstock, which is a wedge-shaped member having a concave face that can “steer” a mill or cutter to a side of the wall where the lateral wellbore will be formed. The whipstock may be run in by itself or, to save a trip, the whipstock might be run in with the mill or cutter temporarily attached to its upper edge. In either case, the whipstock has to be oriented and secured in the wellbore in order to properly direct the milling operation.
There are various means of orienting and securing a whipstock in a wellbore. For example, a retaining device, such as a packer or a seat, and an orientation device, such as a stinger disposed at the bottom of a whipstock, may be used to set the whipstock in a wellbore. Typically, the stinger device includes a splined arrangement that is configured to engage the retaining device previously disposed in the wellbore. Upon engagement of the splined arrangement with a packer or seat, the whipstock is rotated from the surface to a predetermined orientation where the lateral wellbore will commence. In order to rotate the whipstock from the surface, it is necessary to run the whipstock in on a jointed pipe in order to transfer rotation from the surface to the downhole location.
It is often necessary to remove a whipstock from a wellbore. A retrieval tool is used to retrieve a whipstock from a wellbore. The retrieval tool is run into the wellbore on jointed pipe and positioned adjacent the whipstock. A drilling rig is required to assemble the pipe as the tool is run in and to disassemble the pipe as the tool is removed. The retrieval tool is then rotated and manipulated from the surface until it couples with the whipstock. The retrieval tool is then removed from the wellbore along with the whipstock.
The use of jointed pipe is costly and time consuming. Continuous conveyances, such as wireline, are cheaper and less time consuming. However, due to the flexible nature of these conveyances, there is no effective way to transfer, manipulate, and rotate the retrieval tool in order to engage the whipstock.
Therefore, there is a need for a retrieval tool that is self aligning with the whipstock in order to be run into the wellbore on a flexible conveyance. There is a further need for a method and apparatus for setting a whipstock in a wellbore using a flexible conveyance, such as a wireline.